Synthesis and characterization of (Fe3O4/PVA)/SiO2 magnetic nano-compositions with core-shell structure

SiO2/Fe3O4 magnetic nanocomposition (Fe3O4 nanoparticles core coated by SiO2 shell) have the wide promising applications in biomedical field and have usually been prepared based on the famous Stober process. However, the flocculation of Fe3O4 nanoparticles easily occurred during the coating of silica, which further limits the amount of magnetic silica particles produced in the Stober process. In this paper, Fe3O4/PVAc nanocompositions obtained by miniemulsion polymerization of PVAc were used in the stober process instead of the "pure" Fe3O4 nanoparticles. Here, PVAc prevents magnetic nanoparticles from the aggregation that usually comes from the increasing of ionic strength during the hydrolyzation of TEOS by the steric protection. The results show that the coating of Fe3O4 by PVAc polymer beforehand can increase the critical concentration of magnetic nanoparticles in the Stober process. In order to characterize (Fe3O4/PVA)/SiO2 nanocompositions, transmission electron microscopy (TEM) were employed. According the image of TEM, the morphology is obviously core-shell structure: the average diameter of Fe3O4/PVAc is 200 nm; the average diameter of (Fe3O4/PVA)/SiO2 is 500 nm. Because of the versatile surface functionalities, its applications in biosciences, such as protein and enzyme, immunoassay and DNA purification, cell isolation, and target drug, is promising.